about metaWeblog.newPost

when I post xml like below to "https://storage.msn.com/storageservice/MetaWeblog.rpc",it response 400 and "bad request".So who knows why

<methodCall><methodName> metaWeblog.newPost</methodName><params><param><value><string>MyBlog</string></value></param><param><value><string>lawfirm</string></value></param><param><value><string>7648530</string></value></param><param><struct><member><name>categories<value><array><data><value>Adventures</value></data></array></value></name></member><member><name>description</name><value>Dr. Quest is missing while on an expedition to find the Yeti. Jonny and his friends head to the Himalayas to find him, but run into another scientist who's determined to bring back the Yeti.</value></member><member><name>title</name><value>Expedition To Khumbu</value></member><member><name>dateCreated</name><value>20040716T19:20:30</value></member></struct></param><param><boolean>1</boolean></param></params></methodCall>